…GMI Ratings, a corporate-governance research firm, looked at the impact of splitting the top jobs on shareholder returns and other considerations in a study published last June. The research found total shareholder return at companies where CEO and chairman posts were combined outperformed those where the positions had been separated after one year (returns of 12% compared with 2.3%) and after three years (returns of 104% compared with 95%). The reverse was true after five years, when companies with split roles returned 40% and companies with combined roles returned 31%. The figures track appreciation in share price plus reinvested dividends.

“One possible reason is that a CEO unopposed by an independent chairman may find more freedom to make decisions in a way that immediately benefits the company,” authors Paul Hadgson and Greg Ruel wrote. “These aren’t always the decisions, however, that lead to a successful long-term model…”